Fish thaw. Clean and wash the cabbage and remove 8 large outer leaves. Blanch cabbage leaves in portions in boiling water for about 2 minutes, then drain. Cut midribs flat. Use remaining cabbage for other purposes
Cut slightly frozen fish into pieces, except for 2 fillets. Season with salt and pepper. Puree half of the fish cut into pieces, add 1 egg white and approx. 75 g cream, mash with and put into a large bowl. Process the remaining fish cut into pieces, 1 egg white and 75 g cream in the same way
Clean and wash spring onions, shake dry and cut into 9 cm long pieces and slice lengthwise. Cut remaining salmon fillets once horizontally and then vertically into quarters. Wrap a piece of spring onion around each salmon. Spread the salmon farce on the cabbage leaves, leaving a margin of approx. 2 cm at the top and bottom and approx. 3 cm at the sides. Place the wrapped salmon fillets widthways on the salmon farce, fold in the side edges of the cabbage, roll up the cabbage.
Wrap the cabbage rolls in foil, twisting the ends together. Bring a large pot of water to the boil, carefully add the rolls and poach in boiling water for about 30 minutes.
Peel and finely dice the onion. Wash the dill, shake dry and chop coarsely, except for the 4 dill tips. Melt butter in a pot and fry onion cubes for about 3 minutes until translucent. Stir in flour and sweat briefly. Add stock and horseradish while stirring. Rinse prawns, dab dry, add, bring to the boil and simmer for about 5 minutes. Season to taste with salt and pepper
Lightly whip 100 g cream with the whisks of the hand mixer and stir into the sauce. Remove roulades from the water and remove foil. Arrange the roulades with the shrimp sauce on plates and garnish with dill tips